Many attempts have been made in the prior art to develop methods and apparatus for providing high density printing, such as the printing of a character or a page at a time. For example, in Cielo U.S. Pat. No. 4,275,290 a thermally activated liquid ink printing head is disclosed having a plurality of orifices in a wall of an ink reservoir, with the ink being retained in the orifices by surface tension. Electrical heating elements are included within each ink chamber to heat all of the ink in the orifices, for causing the ink to flow from the orifices to a paper sheet positioned adjacent thereto. It is further taught that the orifices may extend in a line across the head or may be in other predetermined patterns, for printing entire characters at a time. The ink may be transferred to the paper in a completely or partly vaporized state, and may be of a composition that permits heating current to flow through the ink. Alternatively, the application of the heat is used to reduce the surface tension of the ink within the orifices, causing the ink to move out of the orifice being heated. Another Cielo U.S. Pat. No. 4,164,745 discloses the selective heating of ink under constant pressure in a reservoir, for modlating the viscosity of the ink to control the volume of ink ejected from an associated orifice.
A printer providing an electrostatic capillary apparatus is disclosed in Bettia U.S. Pat. No. 3,750,564, wherein a printing surface is provided by a plurality of capillary media filled with writing liquid, for accomplishing printing by positioning a recording carrier adjacent the capillary media, and causing electrokinetic movement of the writing fluid from the capillaries to the recording carrier via the application of a voltage across the capillary media.
In Hendricks, Jr. U.S. Pat. No. 3,545,374, entitled "High-Speed Printer Employing a Discharge Matrix", a perforated insulator material is provided with electrodes within each perforation to initiate ionization of a gas therein via selective application of an electrical signal, whereby the gas so produced is maintained in an ionized state by an electric potential connected between outer electrodes. A web is placed across open ends of the perforations for receiving the ionized gas emitted from the perforations for imprinting a pattern upon the web.
In Naiman U.S. Pat. No. 3,211,088, a non-contact printer is disclosed which includes a matrix of individual print means for printing individual dots therefrom in a desired pattern determined by appropriate selection of the individual print means during a printing cycle. The individual print means are provided by apertures bored into a mounting surface, whereby each aperture is in the form of an exponential horn with the small end of the horn at the exit hole on the mounting surface closest to the surface which is to be printed upon. The opposite end of the horn, of each printing means, having the largest diameter of the horn, is immersed in ink, whereby a pressure producing transducer is placed in the ink below the horn portion, and selective ones of the transducers are energized for producing a pressure wave for causing ink to be jetted from the smaller ends of the selected ones of the exponential horns to the under surface of a paper being held adjacent these smaller ends for printing upon the paper.
No one or combination of the above-indicated references teach or even allude to methods or apparatus for using a phase-change ink, which is solid at room temperature and liquid at some elevated temperature above room temperature, in a high density array printer.